import {z} from 'zod'

export type GetApiV3SignalIndexArgs = {region: string, signal_type: 'co2_moer'};

export type GetApiV3SignalIndexOptions = {baseUrl?: string | undefined, BearerAuth?: string | undefined, fetch?: typeof fetch | undefined};

export const baseAPIV3ResponseFormat = z.object({point_time: z.string(), value: z.number()});

export const warningType = z.object({type: z.string(), message: z.string()});

export const modelTypes = z.enum(["interchange", "average", "binned_regression", "heatrate", "proxy", "synthetic_proxy", "forecast", "synthetic_vre_potential"]);

export const v3ModelMetadata = z.object({date: z.string(), type: modelTypes.nullable().optional()});

export const v3SignalIndexMetadata = z.object({data_point_period_seconds: z.number().int(), region: z.string(), signal_type: z.literal("co2_moer"), units: z.string(), warnings: z.array(warningType), model: v3ModelMetadata.nullable().optional()});

export const v3SignalIndexForecastResponse = z.object({data: z.array(baseAPIV3ResponseFormat), meta: v3SignalIndexMetadata});

export const validateResponse = async <Output>(
  schema: {
    readonly '~standard': {
      readonly validate: (value: unknown) => ({ readonly value: Output; readonly issues?: undefined } | { readonly issues: ReadonlyArray<{ readonly message: string; readonly path?: ReadonlyArray<PropertyKey | { readonly key: PropertyKey }> | undefined }> }) | Promise<{ readonly value: Output; readonly issues?: undefined } | { readonly issues: ReadonlyArray<{ readonly message: string; readonly path?: ReadonlyArray<PropertyKey | { readonly key: PropertyKey }> | undefined }> }>
    }
  },
  value: unknown
): Promise<Output> => {
  const result = await schema['~standard'].validate(value)

  if (result.issues !== undefined) {
    const detail = result.issues
      .map(({ message, path }) =>
        path?.length
          ? `${path.map((segment) => String(typeof segment === 'object' ? segment.key : segment)).join('.')}: ${message}`
          : message
      )
      .join('; ')

    throw new Error(`Response does not match the schema: ${detail}`, { cause: { issues: result.issues } })
  }

  return result.value
};

/**
 * Get the current CO2 MOER index
 * 
 * GET /v3/signal-index
 */
export const getApiV3SignalIndex = async (args: GetApiV3SignalIndexArgs, options?: GetApiV3SignalIndexOptions) => {
const {baseUrl = "https://api.watttime.org", fetch: fetchFn = fetch, BearerAuth} = options ?? {}

const query = new URLSearchParams()
const headers = new Headers()
headers.set('accept', "application/json")

if (args.region != null) query.append("region", String(args.region))
if (args.signal_type != null) query.append("signal_type", String(args.signal_type))
if (BearerAuth !== undefined) headers.set('authorization', `Bearer ${BearerAuth}`)

const url = `${baseUrl.replace(/\/+$/, '')}/v3/signal-index${query.size > 0 ? `?${query}` : ''}`

const res = await fetchFn(url, {method: "GET", headers})

if (!res.ok) throw new Error(`Request failed with status ${res.status}`, {cause: {status: res.status, body: await res.text()}})

return validateResponse(v3SignalIndexForecastResponse, await res.json())
};